OFFSET
0,2
COMMENTS
a(n) >= ceiling(n*(n + 1)*(2n + 1)/3).
LINKS
Erich Friedman, Dominoes in Squares
FORMULA
a(n) = A237886(n)^2.
EXAMPLE
Illustration:
.
. - - a - - - a a - - - - - - - - a a b b
. a a a - - - b b b b - - c c c c c c b b
. b b b b b b b b - - c c c c c c b b
. b b b b c c c c c c c c c c c c b b
. c c c c c c d d d d d d d d
. c c c c c c d d d d d d d d
. d d d d d d d d
. d d d d d d d d
.
. 4 16 36 64
.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Ivan Panchenko, Feb 21 2014
STATUS
approved